One well known technique to enter one or more pages of a document into a document processing system employs a document imaging system, such as an optical scanner, to sense differences in optical density that occur on a surface of a page. The differences in optical density are converted to binary information (pixels) at a predetermined or selected resolution, such as 200 dots per inch (dpi), and are output in a scanline format. The document image data can be displayed to a user of the system. The image data may also be subsequently compressed, and/or it may be further processed to identify an informational content of the scanned image. Optical character recognition (OCR) is one well-known processing technique that is used to convert groups of image pixels to codes that correspond to alphanumeric characters.
A user of a document imaging system often finds it desirable to select a portion of text from a scanned binary bitmap image of the text. The selected portion can then be processed to perform, by example, OCR, de-skewing, cut-and-paste, redaction and/or other such processes. A most convenient interaction, from the user's point of view, would be to identify the desired processing operation and to then simply point with, by example, keyboard arrow keys, a mouse, or a trackball, to the starting and ending points of the selected text portion in the display of the bitmap image.
In response to the user's input, it would also be desirable to invoke a program to refine the user's approximate geometric specification of the implied portion of the bitmap, thus determining the leftward and rightward extents of the implied portion and also the period and phase of lines of text within the implied portion, in addition to a slope (deviation from exactly horizontal) of the bitmap image. That is, the task of the program would be to perform a five-dimensional search through combinations of possible values of these five parameters, within an interactively acceptable time period, yielding the refined geometric specification of the selected portion of the bitmap image. The refined geometric specification could then be passed to another routine, such as a cut-and-paste routine, which would then accurately locate the desired portion of the text in the bitmap image to perform the desired operation.
Heretofore there has not existed a document processing system capable of executing a sequence of automated operations for performing such a five-dimensional search, at an interactively acceptable speed, and for outputting a refined geometric specification.